Machines such as a wheel loaders, scrapers, track-type tractors, on and off-highway haul trucks, motor graders, and other heavy equipment generally include hydraulic systems that facilitate different operations of the machines. Typical hydraulic systems include hydro-mechanical actuators known as cylinders. The cylinders are usually supplied with hydraulic fluid from a fluid tank mounted on the machine. The hydraulic fluid travels through a series of conduits, connections, channels, and valves from the fluid tank to the cylinders and from the cylinders back to the fluid tank.
In some situations, it may be possible for a cylinder to move faster than the rate at which hydraulic fluid can be supplied to the cylinder to move the cylinder. For example, the cylinder can be connected to a tool that, when heavily loaded, causes the cylinder to retract faster than would normally be caused by the hydraulic fluid. In these situations, the rapid travel of the cylinder can create air voids in the cylinder at one end. Air voids can result in damaging pressure extremes and oscillations that can reduce the durability, reliability, and efficiency of the machine.
Reducing air voids in hydraulic systems is often accomplished by creating resistance to the hydraulic fluid draining from the cylinder (i.e., backpressure), by restricting the flow of hydraulic fluid. This can be achieved by placing specialized restrictive orifices at discrete locations within the hydraulic system. The generated backpressure can be used to operate a valve that redirects oil to the end of the cylinder containing air voids. An exemplary system utilizing restrictive orifices in this manner is described in U.S. Pat. No. 3,589,387 that issued to Raymond on Jun. 29, 1971.
Although utilizing restrictive orifices may help create desired backpressure, it may be less than optimal. This is because the use of restrictive orifices may necessitate mounting where it is inconvenient to do so. It may also require breaking continuous portions of the conduits, connections, and channels carrying the hydraulic fluid into multiple sections to provide a location for the restrictive orifice. Additionally, rather than facilitating a gradual pressure drop across the hydraulic system, the use of restrictive orifices may induce a sharp pressure drop at a discrete location (i.e., the location of the restrictive orifice). This sharp pressure drop may result in an elevated release of energy and heat over a short distance, which can overheat the surrounding area and the hydraulic fluid.
The hydraulic system of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.